My father had a small 20 gallon salt water aquarium. The fish in the aquarium died about 4-5 month ago. But my father never emptied the aquarium, however the water evaporated about half way. So there was only about 10 gallons of water in the 20 gallon tank.

When I measured the salinity, it was about 1.32 - so I filled up the tank, making the salinity approximately 1.24.

What do these results indicate? Does this mean I can add a fish (after I lower the PH of course)? How much longer should I wait.

The reason I ask is that I didn't really add anything that causes ammonia, so techically the tank should be fish ready.

Pasfur

09-01-2008 05:34 PM

First, your Nitrate readings are out of control. 40ppm is generally the top that is acceptable for a fish only aquarium. Temporary readings of 80ppm might be tolerated. But you have to do a very large water change before considering any livestock.

karaim

09-01-2008 06:51 PM

Thanks. I will do several water changes over the next couple of days.

I am wondering if I have any bacteria in the tank. Since there has been no fish for the past 4-5 months and the salinity has been 1.032, is it possible that some bacteria survived?

I also have a general question about cycling a tank. From what I understand, there is bacteria that turns ammonia into nitrite and there is bacteria that turns nitrite into nitrate. During live rock curing, there is some die off and then some ammonia, which allows bacteria to grow to eat the ammonia. But what happens after the ammonia is gone? Does the bacteria that turned the ammonia into nitrate die off since it has nothing else to feed on?

Oh and 1 more question - aside from water changes, what else can I do to lower nitrates? I know that live plants eat nitrates, but what plants can I get for saltwater? Doesn't algae also consume nitrates?

Pasfur

09-01-2008 07:46 PM

Live plants and algae in a marine aquarium are generally not adequate for Nitrate removal, and are not utilized by most hobbyists.

If you set the aquarium up properly, you will have a 3'' layer of aragonite sand, live rock, and a protein skimmer. The protein skimmer will remove the majority of the organic waste. The remaining waste will be consumed by the live rock, which processes ammonia > nitrite > nitrate > nitrogen gas. The nitrogen gas leaves the system naturally, and still no nitrate has accumulated. There will be small amounts of nitrate accumulation which results from organic acids that bond to other substrates within the aquarium, and these organics will break down into Nitrate. The aragonite sand bed serves as a denitrification system which removes Nitrates naturally from the aquarium.

I am guessing that the aquarium your father had was set up with a biological filter, such as a biowheel or undergravel filter. This is not the preferred method of setting up a marine aquarium and is a high-maintenance system. It is also much more expensive to upkeep, because it will require much larger and more frequent water changes.

My suggestion is to add aragonite sand to the aquarium and add a protein skimmer. Then add a couple more pieces of live rock to seed the aquarium. This should be sufficient to cycle the aquarium properly.

Prior to doing this, I suggest a single 90% water change.

karaim

09-01-2008 10:16 PM

Thaks again for your help.

You're right, my father has an undergravel filter. I will remove it tomorrow. But just out of curiosity, how does an undergravel filter or other biowheel filters increase nitrates?

Also, I thought the last stage of the nitrogen cycle was nitrate production. There are actually bacteria that eat the nitrates and transfer it to nitrogen?

Pasfur

09-02-2008 07:35 AM

Quote:

Originally Posted by karaim

Also, I thought the last stage of the nitrogen cycle was nitrate production. There are actually bacteria that eat the nitrates and transfer it to nitrogen?

You answered your own question, as far as the u/g is concerned.

And yes, denitrification can be achieved in saltwater. This is achieved with live rock and a sand bed of 3'' to 4'' depth. It should be noted that denitrification is rarely achieved at depths below 3''. Do not skimp on this amount, or you could have a potential disaster on your hands long term.

karaim

09-02-2008 09:42 AM

I was planning to do a 4 inch DSB. How much sand would I need to get 4 inches in a tank that's 60 (length) x 18 (depth)?

Also I was looking at CaribSea Fiji Pink, but the company says this sand isn't safe for burrowing animals. Should I go for something that is safe for burrowing animals?